The European College of Equine Internal Medicine define Equine Metabolic Syndrome or EMS as “a collection of risk factors for endocrinopathic laminitis”. 

Probably the most important of these risk factors is insulin dysregulation (ID) – sometimes referred to as hyperinsulinaemia, when insulin levels remain higher than normal in the horse or pony’s body.   Your Vet will advise you on the testing required to determine your horse or pony’s insulin status.

As well as Insulin dysregulation, obesity is another risk factor usually (but not always) associated with EMS. It is important to remember that not all horses and ponies with one or more of the risk factors will develop laminitis, and we don’t always understand how these risk factors cause laminitis in susceptible individuals. There may be genetic influences and there is certainly variation between individuals – there is still much more to learn!

However, we do know that careful management of horses and ponies with EMS is vital, and will require a long term, disciplined approach from all those involved in the care of the horse, including the owner or yard manager, the Vet, the Farrier, the Nutritionist and others.

Management strategies to help control EMS involve mainly diet and exercise regimes designed to reduce obesity and improve insulin regulation. There are some medications that may also help in cases where weight loss is proving difficult, despite the introduction and maintenance of strict dietary controls, and your Vet will advise you on whether these medications are suitable or required as part of the overall management programme.

Dietary strategies to help with weight loss  and improve insulin sensitivity involve restricting energy intake, typically through the removal of high energy, high starch and sugar feeds, and sometimes even the removal of high sugar fruits and vegetables from the diet. A forage-based diet is required, often restricting or even removing access to pasture, as this can also be too high in sugar and/or energy (calories) for many EMS affected horses and ponies on a weight loss regime.

The use of well-fitting grazing muzzles, or controlled track grazing systems work well for some horses and ponies, allowing time at pasture for normal grazing behaviour, socializing (where appropriate) and exercise, although some horses and ponies will require complete removal from grass for grazing to facilitate weight loss.

There is a fine line between providing enough forage to meet gut motility, chewing time to produce saliva to help support stomach health, (plus psychological requirements)- and the need to restrict intake to encourage weight loss. It is generally recommended that around 1.5% of bodyweight of dry matter forage should be the initial aim, adjusted as required for individuals, and divided up into a suitable number of meals offered throughout the 24 hour period, as practical in your management situation, and under guidance from your Vet or Nutritionist. The use of small-holed nets or other strategies to reduce intake, encourage normal behaviours and prolong eating time will probably need to be considered, especially for those on restricted or zero grazing regimes.

Forage with a low (ideally under 10% ) Non Structural Carbohydrate (NSC) level is preferable, usually achieved through soaking to help to reduce the Water Soluble Carbohydrate (WSC) level. Once again, there are differing recommendations on suitable soaking times, as longer soaking times to reduce more WSC can result in microbial activity or fermentation in the soaking water, especially in warmer weather. So it is generally recommended that hay should be soaked for 1-2 hours, rinsed after soaking, and soaking water changed for each use in warmer weather, perhaps increased to up to 4 - 6 hours in the colder months for maximum effect.

Because soaking removes many nutrients, additional minerals and vitamins will be required for all restricted horses and ponies, and this can be provided through a powdered, broad spectrum mineral and vitamin supplement, offered in a small feed of low sugar chaff. Balancer pellets or mineral and vitamin fortified treats could also be considered, and horses and ponies in harder work will probably need additional protein and possibly a non-starch/sugar source of additional energy such as oil to enable them to work at the desired level.  A suitable programme to support the increased nutrient demand for EMS horses and ponies in harder work should be discussed with your Nutritionist or Vet.

The use of a weight tape may be helpful to monitor weight loss objectively, and the aim should be for approximately 0.5 – 1.0% bodyweight weight loss weekly. Regular Body Condition Scoring can also be an objective method of monitoring weight loss progression.

Exercise Regimes will also help reduce weight loss and improve insulin sensitivity, but must be considered in the light of current or recent laminitis episodes, and always discussed with your Vet in these cases. All exercise regimes should be gradually introduced when appropriate, and closely monitored, especially in horses or ponies who have previously had laminitis, to help prevent further damage to the lamellar structures.

It’s important to maintain ongoing discussions with your Vet to ensure regular endocrine monitoring, as well as vigilant checking for signs of laminitis, in addition to  maintaining a strict obesity control regime to help ensure the well-being of your horse or pony with EMS.

(Endocrinopathic laminitis is caused by disruption or disturbance to the endocrine or hormone systems in the body, including insulin dysregulation and Cushings Disease (PPID). There are of course, other causes of laminitis, but endocrinopathic causes are thought to be the most common in horses and ponies in the UK, partly due to high levels of obesity - especially in leisure horses and ponies.) 

Written by Debeorah Leabeater MSc CBiol MRSB.

Reference
ECEIM Consensus Statement on Equine Metabolic Syndrome

Andy E. Durham, Nicholas Frank, Cathy M. McGowan, Nicola J. Menzies-Gow, Ellen Roelfsema, Ingrid Vervuert, Karsten Feige, Kerstin Fey

Journal of Internal Veterinary Medicine Volume33, Issue2 March/April 2019 Pages 335-349